The present invention relates to an energy recovery apparatus for a turbocharged compound engine capable of recovering the exhaust energy of an internal combustion engine and, more particularly, to an energy recovery apparatus for a turbo compound engine for recovering the exhaust energy by controlling an AC machine driven by the exhaust energy and an AC machine mounted on a wheel axle.
There have been developed, in recent years, thermally insulated engines having various components made of ceramics, including an outer wall of an exhaust manifold, a cylinder liner, an insulating plate for a cylinder head, and a piston, for example. In such thermally insulated engines, it is not necessary to cool the engine by radiating the heat generated inside the engine, but the energy from a high-temperature exhaust gas, discharged by the engine, is recovered and fed back to the output shaft of the engine, for increasing the output power from the engine.
One known method of recovering the exhaust energy of an engine utilizes a multistage gear speed reducer mechanism for reducing the speed of rotation of a turbine which is driven by the exhaust gas, and using this recovered energy to rotate the crankshaft, thereby increasing its output power.
Japanese Laid-Open Patent Publication No. 59 (1984)-141713 discloses an exhaust energy recovering device. According to the disclosed device, the exhaust turbine of an AC generator is rotated by the energy of an exhaust gas discharged from an internal combustion engine. An induction motor is operatively coupled to the output shaft of the engine and is driven by the output of the AC generator, thereby recovering the exhaust energy. The device also includes means for determining the magnitude of a load on the engine in order to control the amount of intake air, so that the temperature of the exhaust gas can be increased when the engine load is small.
In the former method of recovering the exhaust energy, the transmission efficiency of the gear mechanism is low and the gear mechanism is complex, which results in an increased cost.
According to the latter exhaust energy recovering device, the electric power generated by the AC generator is utilized to rotate an induction motor, thus driving the output shaft of the engine. There is no gear mechanism required and the amount of intake air is controlled by the engine load for recovering the exhaust energy more efficiently. However, it is desired to control the amount of generated power according to the engine load, and to charge the battery with the generated power.